The subject matter disclosed herein relates to the art of monitoring systems and, more particularly, to a structural integrity monitoring system.
Removing a piece of equipment, such as a turbomachine, generator, or the like, from service in order to perform routine inspections, or to conduct vibration testing to assess structural integrity, is very costly. The costs accrue not only in terms of lost revenue and actual disassembly, but the inspections and tests are themselves costly. However, failure to perform the inspections, and particularly the tests, could lead to significant and hence even more expensive failures. That is, in general, turbomachines, generators, and the like, are subjected to strenuous loads, harsh operating environments and conditions that, over time, lead to deterioration of certain components. Failure to detect this deterioration can result in machine failure. Significant failures of the machine would far outweigh the costs associated with inspection and testing.
One method employed to detect deterioration is to test structural integrity of system components. Online vibration monitoring is commonly used to detect structural integrity defects. However, when using online vibration monitoring, it is sometimes difficult to determine if changes in vibration (increasing or decreasing) are the result of changing loads on the structure, expected changes in structure, or the result of deterioration of the structure. Other types of structural integrity tests include modal vibration testing.
Modal vibration testing of structures typically requires that the structure to be tested be removed from service. In one such testing technique, actuation devices are permanently mounted to the structure. The actuation devices are operated to mechanically excite the structure. Once excited, vibration measurements are taken and compared against baseline measurements to check the integrity of the structure. Still other forms of vibration testing include setting vibration alarm levels and shut down levels. However, such systems cannot distinguish between vibrations that occur as a result in changes in loads from vibrations that occur as a result of changes in the structure.